1. Field of the Invention
This invention relates to a nozzle of a manipulator used to insert a cable with a sensor into various heat exchanger pipes in nondestructive inspection of these pipes.
2. Description of Prior Art
Nondestructive inspection of heat exchanger pipes provided in the thermal and nuclear power plants is generally performed by the use of either the ultrasonic flaw detection method or the eddy current examination method, and in either method, a cable with a float, having a sensor at its point, is inserted into the heat exchanger pipes from their respective ends with the aid of pressurized water or compressed air to perform inspection.
FIG. 6 shows the state in which a cable with a float having been inserted in one heat exchanger pipe is going to be withdrawn through a nozzle of a manipulator press-attached to one pipe end section of the heat exchanger pipe (or to a tubesheet) by application of a back pressure. Of course, a nozzle similar to the above is press-attached to the other pipe end section opposite to that shown in FIG. 6 to apply the back pressure thereto. One conventional configuration will now be described with reference to FIG. 6. In FIG. 6, after heat exchanger pipes 1 are inserted in the counterbore section of a tubesheet 2, they are seal-welded as indicated by reference numeral 3. The nozzle section of the manipulator is a ball and socket joint split into a female segment 4 and a male segment 5, these segments are joined together by the use of a nozzle cap 6 and cap screws 7, and a rubber packing 8 is bonded to the sheet face of the female segment 4 to prevent leakage of pressurized water or compressed air. To a cable 9 is attached a float 9a for generating thrust which is effective in conveying (inserting and withdrawing) the cable. In short, the feature of the conventional nozzle is that it is split into two segments and a spherical seat is provided. By the configuration as above, it is easy to insert the nozzle in the pipe end section (hole section) even when the center of the nozzle is dislocated owing to flexure of the manipulator and the like.
However, the spherical seat shown in FIG. 6 tends to create a step at a portion of the spherical seat (in the inner face of the nozzle). Hence, the float 9a is sometimes caught in the course of conveying (inserting and withdrawing) the cable and conveying of the cable becomes unattainable.